This invention relates to a torque limiter which can be built in a rotation-transmitting coupler and is used to protect an input element against the excessive load by breaking the transmission of rotation to an output element. More particularly, this invention relates to a torque limiter which is able to break the rotation transmission from an input element to an output element by the control of balls.
So far there have been used many types of torque limiters different in structure in order to transmit rotation and protect an input element against an excessive load given to an output element; therefore, it is well known that balls are used to control the breaking and resuming of the transmission.
Conventional torque limiters which employ balls for the above objective are constructed with a ring plate with holes therethrough for holding balls which is fixed to and rotates in association with an output element, a flange provided with tapered holes that allow the balls to enter and exit the tapered holes is united to an input element and a slider to press the balls against the flange across the ring plate is fitted on the input element so as to be movable freely thereon. A pair of tapered bars are put between the slider and the input element; a plurality of balls are placed between the two opposing tapered bars; and a compressed spring is provided for one of the bars. By the construction the balls are pressed between the bars and biased away therefrom. The balls fix the slider in an advanced position when they are out of or not between the bars in order to transmit rotation from the input element to the output element and the balls fix the slider in a retired or retracted position when they are let in or are between the bars to widen them in order to break the rotation transmission.
In a conventional torque limiter like this, the balls are kept in point contact with the tapered bars; thus, an acting load is concentrated on the point of contact; hence there has been a problem that the balls and the tapered bars are liable to wear down by repeatedly applied loads.
Under the circumstances, it is an object of this invention to provide a torque limiter in which the concentration of acting loads due to the point contact is avoided so as to greatly lessen the wearing of the balls and the tapered bars. It is another object of this invention to provide a torque limiter whose life and durability are greatly improved due to the remarkable lessened wearing.